Primary immune deficiencies (PIDs) are a group of rare disorders of the immune system, resulting in increased susceptibility to infections, autoimmunity and malignancies. The most severe forms of PIDs are fatal, unless immune reconstitution is achieved by hematopoietic cell transplantation (HCT), enzyme replacement or gene therapy. Because of the many disease- and treatment-related variables that may affect outcome after HCT, both careful collection of data in Registries and multicenter collaboration are needed to facilitate analysis of outcome and development of prospective clinical trials. In 2009, the Primary Immune Deficiency Treatment Consortium (PIDTC) was established in North America with the goal of building a nation-wide collaboration to carry-out retrospective, cross-sectional and prospective studies that would define risk factors, long term outcomes and late effects in children with Severe Combined Immunodeficiency (SCID), Wiskott-Aldrich Syndrome (WAS) and Chronic Granulomatous Disease (CGD) who receive HCT or other forms of treatment. The proposed annual PIDTC Scientific Workshop will represent a unique and critical forum to assemble experienced and young investigators from all major centers in North America involved in the treatment of these disorders, as well as biostatisticians and Patient Advocacy Groups. The PIDTC Workshop will focus on timely topics to facilitate development of clinical trials aimed at improving treatment of PIDs. The specific objectives of the workshop are as follows: 1) To disseminate information on survival, clinical status, and immune function in patients with severe PIDs who have received HCT or other forms of treatment 2) To initiate data collection and analysis in other forms of severe PIDs that can be treated by HCT 3) To analyze the relevance of biological markers that can predict successful immune reconstitution following HCT 4) To discuss the results of novel approaches to HCT for PID that may minimize transplant-related toxicity while allowing robust and durable engraftment and immune reconstitution 5) To discuss newborn screening for SCID and develop protocols for treating newborn infants diagnosed with SCID. 6) To prompt development of clinical trials in the field of HCT for PIDs 7) To promote education of young investigators with a specific interest in treatment of PIDs 8) To increase synergy among Patient Advocacy Groups actively involved in PID awareness campaigns